Billions of Plastic Pieces Litter Asia's and Australia’s Coral

Joleah Lamb began her career as a coral biologist on the Great Barrier Reef. Every now and then she’d note a scrap of plastic as she swam through. But when she started studying reefs in Asia, she came across a completely different level of detritus.

“I don’t even know how to record this!” she remembers thinking. “It’s a chair! Where do I put ‘chair’? Or diaper? Or bottle?”

Over the years, Lamb, who is now a professor at Cornell University, and her collaborators assembled a formidable database of plastic pollution on 159 reefs in Australia, Indonesia, Myanmar and Thailand. In a paper released in the journal Science on Thursday, they estimate that reefs across the Asia-Pacific region are littered with more than 11 billion pieces of plastic larger than 5 centimeters.

If those pieces were lined up next to each other, they would reach around the Earth nearly 14 times, at the very least. To make matters worse, corals with plastic on them were 20 times more likely to be diseased than those that were not polluted.

In their survey of about 12,000 square meters of reef, the researchers noticed that countries that are known to have particularly poor methods of dealing with plastic pollution had the most plastic on corals. By combining the amount of plastic entering the ocean in each country — a known quantity from previous researchers’ work — with their own observations, they were able to estimate how much plastic was likely on reefs in 15 nations in the Asia-Pacific region.

That gave them the stunning figure of 11.1 billion pieces, which they project will increase to 15.7 billion in the next seven years, as worldwide plastics entering the ocean are projected to increase tenfold (the numbers do not include China and Singapore, for which they were not able to make estimates).

Furthermore, when the researchers found plastic on coral, about 90 percent of the time they saw clear signs of disease. There may be several different reasons. To start with, plastic in the ocean is a magnet for bacteria, including some implicated in coral diseases. Polypropylene, used in numerous products like bottle caps and toothpaste tubes, is beloved by the Vibrio group of bacteria, which are behind one set of illnesses.

Even worse, bacteria adds weight to pieces of plastic, making them more likely to fall to the seafloor and land on a reef. Plastics can also block the light, making corals more susceptible to a darkness-loving disease called black band. And once they land, they can wound the coral, making it easier for infection to start.

In fact, the researchers saw that of the six groups of coral diseases generally found on reefs, four were overwhelmingly represented in plastic-contaminated corals, suggesting that those are encouraged by the pollution.

Still, the study shows that it is possible to control the impact of plastic on reefs. Countries that take a great deal of care to keep plastic from entering the ocean — like Australia — see notably lower levels of it on reefs, and the problem was worst in those with poor infrastructure for managing waste, like Indonesia.

Helping those countries manage their pollution, “can also reduce the amount of plastics we’re finding on the reefs there,” Lamb said.

As governments work to try to protect reefs from the threat of climate change and warming waters, she added, addressing plastic pollution must be on the agenda, or those efforts could be less effective.